Electrical measuring apparatus



July 1, 1930.

P. M. F. DUGIT ET AL snacmm. mmsuame armmus Filed Jan. 1:5, 192a 3 Sheets-Sheet 1 July 1, 1-930. P. M.'F. DUGIT U- ILECTRICAL MEASURING APPARATUS 3 Shuts-Sheet 2 Filed Jan. 13

July 1,, 1930. 'P. M. F. DUGlT ET AL 1,769,422

ELECTRICAL MEASURING APPARATUS Filed Jan. 1:. 1928 s Sheets-Sheet 3 Patented July], 1930 mea zz men shame I rareu'rvorrlcs i rrnnnn MAURECE FRANCOIS nuerr, or LYON, Ann AMAIBLE manna JEAN- MARIE rowan-ooze, or sn-n'rrnnms, FRANCE ELECTRICAL MEASURING arrnnn'rus U Application filed January 13, 1928, Serial No. 246,625, and in France January 'lv', 1927 This invention relates to improvements in electric measuring apparatus of the type having a single variable,v for ammeters. volt-.

metres and the like.

Three separate considerations have to be considered.

1. Scales having equidistant readings,

2. Amplifications of the readings,

v 3. An indicating arrangement for multiple reading with distinct scales.

The choice of portions of the integral curves as points onthe equidistant scale .will allow for the employment of equidistant points. g

The amplification of the readings is 01 tained by employing a series of auxiliary curves of the same nature. V p

The third consideration is obtained by the combinationin one, apparatus of indicating systems with independent pointers aifixed to the same spindle, each pointer corresponding to a diilerent scale ofditlerent maXima.

The invention will be described with reference to a portable voltmeter having three gsscales making it possible to, readily indicate separately'voltages of three very different ranges.

The invention will be described with ref-' erence to the accompanying drawings Fig. 1 is a diagrammatic section of an electromagnetic voltmeter having three scale ranges. r Fig. 2 is a detail view of the pointers. Figs. 3, 4: and 5 show plan views of three "forms of the scales. I

Figs. 6 and 7 show diagrammatically the arrangement of the circuits.

Fig. 8 is a front view of the indicating dial and contact members 'for a portable voltmeter but employing the usual arrangement for di-' vision of the points. I

Figs. 9 andlO are diagrammatic viewsof modified circuits.

invention each having three Fig. 11 shows an arrangement employing only two scales.

Fig. '12 shows the plotting of; a curve for obtaining scale readings having equidistant points f Fig. 13 shows diagrammatically a scale ar-. rangement combining two curves of difierent forms. i

v Figs. 14 and 15 are modified arrangements on a circular dial for combining a series "or different curves having equidistant points.

Fig. 16 shows diagrammatically a scale utilizing a main curve and a series of auxiliary curves each having equidistant points.

Figs. 17 and 18 show curves for a particular instrument in which the variations are proportional to the angular displacements of the pointer, a portable voltmet'er'taken as an example is of the pocket type used for testing the cells of accumulators or batteries.

The instrument is constructed with three scale calibrations for example 0 to 120.0 to

6, 0 to 2 volts so that the voltage of different portions of a battery canhe tested as well as that of individual cells. g

.The voltmeter construction is shown in Fig. '1. The apparatus comprises a coilfl inside which is mounted a soft iron core 2 stationary with respect to the coil. A spindie 8 is also arranged within the coil 1 carryinga soft iron armature 4: pivoted at two points 5 and 6 mountedin bearings 7 and 8 respectively. p I V .The spindle 3 carries at its upper end a bracket 9 having four short arms 10, 11.12.

1 on the arms 10, 11 and 12 respectively the pointers being formed-at theends 17 18 and r 19 with arrows or flattened edges or raised ends perpendicular to a dial 20 and a counterweight on the arm 13.

A spiral spring 21 (Fig. 1) returns the pointers to the zero position and during oper- '90 to 6 volt circuit.

ation balances the electromagnetic force between the two masses of soft iron 2 and i.

The dial provided with graduations may be as shown in Figs. 3 and 4 for an electromagnetic voltmeter.

In Fig. 3 the scales are divided in known manner over three arcs of the circumferences of circles concentric with the spindle In Fig. l the 0-120 volt graduation consist of two curves graduated in units. These curves are the integralcurves of the spaces differentiated as will be described hereafter. The O to 6 volt graduation is formed of a series of curves of equidistant points. The O to 2 volt graduation consists of a single curve graduated with equidistant points.

The O to 2 volt graduation is useful for testing individual cells of a battery. In wireless for example, the O to 6 volt raduation serves for testing the voltage applied to the valve filaments and the 120 volt graduation, the tension of the battery.

From the circuit diagrams Fig. 6, it is seen that the coil 1 is formed with two windings 22 and 28 corresponding to the extreme tensions. These windings may be connected in series as shown in Fig. 6 or employed separately as shown in 7. The resistance 24: in series With the winding 22 forms the 0 V The O to 120 volt circuit is formed by thewindings 22 and 23 and the resistance 25 in series as shown in Fig. 6 or by the winding 23 and the resistance 25 7 The O to 2 volt circuit may be formed either through the winding 22 alone or by this winding andan adjustable resistance.

in practice the resistance 24 is short circuited when using the 0 to 6 volt scale. For this purpose the resistance 24 is connected to two terminals 26 "and 27. One terminal 26 is ar'lixed to a switch arm 28.

A push button 29 is provided for operating the arm 28 to bring it into contact With the terminal 27. This operation short circuits the resistance 24land places it on the O to 2 range. One end 30 ofthe coil 22 (O to" 6 volts) is connected 2.0 a terminal 31 as shown 7 in 6. The second end 34 of the coil ..3 is connected to one end 35 of the resistance 25. The second end 36 of the resistance 25 is connected by a terminal 37 to the battery. In a voltmeter of the pocket type the terminal 37 consists of a metal point. The connection to the end 36 is made by a flex- 'ihle cord 38."

The end 32 of the coil 22 and the end 33 of the coil 23 are connected to the terminal 27. nected to the terminal 26. in the pocket type of voltmeter. the lead 39 is a flexible cord and the terminal 40 a metal point. 7

From the foregoing it is apparent that the terminal 31 is common for all three ranges.

Fig. 8 gives a plan View of the indicating arrangement for a pocket voltmeter having i lead 39,.having a terminal 40 is con-.

' graduations are arranged in the ordinary way. A series of auxiliary curves can be employed together .vith the arcs of circles to re resent the scale, these auxiliary curves having equidistant markings. The curves are obtained as Will be described hereafter.

The operation of the three scale voltmeter is as follows tilieasa-remeni 07" tension between 0 and 120 volts The terminal 31 brought in contat with one of the terminals of the clrcuit on test 7 and the point 37 with the second terminal. Current flows through the coils 22 and 23 (Fig. 6) and the adjustable resistance 25.

In the modification shown in Fig. 7 the current does not pass through the coil 22. If an arrangement employing only two inrated curves, as in the case shown in Fig. the pointer 15 gives the value of the test voltage. Theunits of the higher order are shown by the principal graduated scale. The units of the lower orders are obtained by interpolation and that much more easily, in thatthe scales are shown following a linear law so that the eye can easily interpret the reduced readings with great accuracy. 7

This scale of O to 120 volts can also be readily shown on two integrated curves in conjunction with a series of auxiliary curves obtained in the same way as the graduati n for 0 to 6 volts or by an ordinary circular graduation alone or combined with aseries of auxiliary curves.

Measurement of tension between 0 6 colts The point- 31 is brought into contact with one of the terminals and the point l0 with the second. The voltage is read on the scale under the pointer 16. In the case shown in Fig. i the reading is made on one of the auxiliary Ilicasmemeat 0f ten-s'ioa'between 0 and salts The point 31 is brought into contact with The push button 29 is'de'pressed which shortcircuits the resistance in the O to 6 volt circuit and the reading is taken from the scale under the pointer 14. The graduations are calibrated similarly to those for the O to 120 volt range. v D

In the case of moving vane apparatus. a C01l l0) rotatable between the poles on": a permanent magnet (not proportionately to the voltage of the current applied; A. terminal l2 of the coil. is connectec to the contacting point 31 which is common to all'three ranges. To the end 43 the winding; two distinct circuits are conred one 001' "ises a resistance 4%, lead and a cont.w 11g point 416. The second comprises a reels ance all connected between shown) being displaced two terminals-48 and 49. A second resistance 50 one end 51of'whichis connected to the terminal 49 and the other 52 through a lead 53 to contacting point 54.

A flexible switch arm-55 is connected to the terminal 49. A push button 56 is provided to bring the arm 55 into contact with the terminal 48.

The first circuit is employed for. one of the three ranges and the second for the othertWo.

One of the two latter is obtained by employing the winding 41 in series with the resistances 47 and 50 and the other by employing-the winding 41 with the resistance 50 alone, the resistance 47 being short circuited by the arm 55 as described above.

For a voltmeter of the pocket moving vane type, the leads and 54 are flexible cords and the terminals 46 and 54 metal points. The op eration is similar to that of the electromagnetic voltmeter.

The production of the various curves will now be described. The rule governing the system employed is ascertained in the case of each range, the angular displacements of the pointer being a function of the terminal volt- ,age applied. This law is as follows A denotes the voltage,

B denotes the angular displacement of the pointer relatively to an initial position,

F is a continuous function of the variable A considered,

A differential equation is formed for each in which 1 B is the differential of B with respect to C I? is the derived function of F with respect to i,

C the radius vector in co-ordinate pole representation of which the origin is a point coinciding with the needle spindle and the zero ordinate lies along the pointer when in.

its position of rest. I

K is a constant having a value depending on the graduation units. v

The resolution of a differential equation of the general form given above can be represented graphically as is wellknown with great accuracy. If origin (Fig. 12) is represented by a it is found for a given constant 05, of the space curve Z7 (radius vectors ascending with polar angleslis employed. From f to e an arc of the space curve c -(radius vectors descending when the polar angle is inr creased) is employed.

Thegraduation for 0 to 120 volts Fig.4

been calculated bypoints. By calculus the co-ordinates .of the points 40, 50, .60, 70, 80, 90, 100, 110, 120 volts can becalculated directly orif desired, any other points. In this latter case after havingdrawn'the arcs of 7-0 therefor beenfestablished. "The arcs'of the curves 40 to volts and 80 to .120 volts have the curves they can be divided up into equal parts according to the graduationconstant.

This operation is easily done with graduated scales or with curves. The subdivisions of the main pointscorresponding to units is also readily effected.

For clearness on the drawings thegraduationis'not carried beyond14O volts. i

The 0 to 6 Volt graduation starting above 1:

volt is gotten in the samegeneralwayasthat shown in Figs. 12 and Integral curves 1 are made for each interval 1 to 2, '2 .to 3, 3 t0. 1 i

4, 5 to 6 volts to whichthe scale is limited. The'origins 1, 2, 3, 4, 5 of these arcs are respectively situatedon the sameradius vector.

as thefends 2,- 3, 4-, 5, 6 of the arc's.- The radius 5 vectors may be constructed with equal endings as shown in Fig.4. The arcs may be subdivided into ten equal parts eachcorr'esponding to one tenth of a volt. f

F ig. 14 shows a modification in which the auxiliary integral curves have been chosen insucha way as to give radius vectors ascending with the polar angle. In Fig. 15 on the j other handthe arcs are the reverse.

' These sets of auxiliary integral curvesmay becombinedwith circular arcs giving the main points (points corresponding to units of the higher order) in the usual notation.

These are the arcsof auxiliary curves which give the invention novelty by theequal. division of the points corresponding to units of the lower order and of the higher order. Figs. 14 and-15 show this modification.

The principal curve maybe an integral curve as shown in Fig. 16.

On the scales of the types 14, 15 and 16 the readings are taken from theintersect-ion ofv the pointer and the principal curves for the units of a higher order'and the intersection of the needle and one of the auxiliary curves for those of a lower order. I

Returning to Fig. 4 it'is seen that the O to 6 volt needle shows two volts on the main curve and seven tenths on theauxiliary curve.

The 0 to 2 volt graduation is obtained from a single integral curve giving a tenth of a volt on ascale of two centimeters to a'volt- Or may be constructed on other basis.

In the particular case where, the variations are proportional to the angularidisp'lace ments of the needle -(protractors, balances,

galvanometers and the like) the integral curves are circles. r

For a given constant in general there are two integral circumferences passing through a given point. It may be shown according to the choice of constant that the two circum-- ferences are tangential.

Fig. 18shows for an angle 9, h, z'two pairs of circumferences for the same constant but with different origins. The first pairhas an ence is and Z. tangents to j. The circumference '70 has a centre It the circumference Z has a slightly smaller radius. 'The second pair with an origin at corresponds to the same constant and comprises two arcs havlng circumferences n and p botn'passing through the point h. a v

Fig. 16 shows the arrangement of the scale in the case where auxiliary circles are employed. Its reading is similar.

A moving vane voltmeter having an indicator as shown in Fig. 5 and coil connections I lar semi-circumference but the constant is fifteen millimeters per volt.

The O to 120 volt graduation comprises an arc'of 180 of a circle 1. This are forms the main scale with a constant of eight tenths of a millimetre per volt. As in general in using apparatus for wireless telegraphy accuracy inmeasuring voltages of 40 to 80 volts is desired, the sensibility of the readings can be increased. by drawing in the spaces 30-40 volts tO-5O volts/ to volts 80 to volts arcs having auxiliary circumference s, t, u, v.

The arcs s and a corresponding to voltages lower than the critical values are arranged with ascending vectors, the arcs t and 'v with descending vectors as the voltage rises. The constant of these auxiliary circumferential arcs maybe ten millimetres per Volt. As the corresponding circumferences pass. through a known point towhich their origin is fixed they are completely determined and can be constructed from the preceding graphs. In the case of Fig. 5 the three needles constructed as shown in Fig. 2 are calibrated through 120. r

The foregoing apparatusrelates to three ranges but similar apparatus may be constructed for one, two or other ranges.

l/Vhat we claimfas our invention and desire to protect by Letters Patent is a A voltmeter having a plurality of scales a pointer moving over each scale, a common spindle and an armature carrying the spindle upon which the pointers are mounted, two

coils for operating the armature, a resistance in series with each coil, aswitch for cutting out one resistance, and means for employing the two coils in series to give threedistinct ranges over which the apparatus will indicate sensitively.

In witness whereof'we aifix oursignatures.

PlERRE DUGIT. AMABLE PIERRE JEAN-MARIEIFOULHOUZE.

origin comprising two arcs of circumfery 

